Tracker Estimates – Sentinel-3 Altimetry Technical Guide – Sentinel Online
The tracker range is the distance from the satellite to the Earth's surface corrected for instrumental corrections such as USO frequency drift, internal path correction or Doppler correction.
The geophysical corrections are not applied to the tracker range. The AGC (Automatic Gain Control) is the gain applied on-board to the waveforms and corrected for instrumental errors.
The sigma0 scaling factor is used to compute the backscatter coefficient of the waveforms. The sigma0 scaling factor represents a backscatter coefficient for waveform amplitude equal to 1.
PARAMETER |
AGC Corrected Estimate |
NETCDF NAME |
agc_[x1]_[x2] where |
DESCRIPTION |
AGC corrected for instrumental errors (agc_cor_[x1]_[x2])For SAR mode, the correction value is the closest in time to the reference measurement. |
UNITS |
10-2 dB |
DATA SET AVAILABILITY |
Reduced: none |
OPERATING MODE AVAILABILITY |
LRM and SAR |
DATA ORIGIN |
1 Hz Ku/C-bands: ALT_COM_AGC_01 algorithm 20 Hz Ku-band: SRAL Level-1B product 20 Hz C-band: SRAL Level-1B product |
ADDITIONAL INFORMATION |
None |
PARAMETERS RELATED |
Number of valid points to compute AGC (agc_num_val_[x1]_[x2]) |
PARAMETER DETAILED DESCRIPTION |
ESA's Global Land and Ocean Mission for GMES Operational Services |
Table 1. AGC
PARAMETER |
Scaling Factor for Sigma0 Evaluation |
NETCDF NAME |
scale_factor_[x1]_[x2] |
DESCRIPTION |
Scaling factor for backscatter coefficient (sigma0) evaluation. This scaling factor represents the backscatter coefficient for waveform amplitude equal to 1. It is corrected for: |
UNITS |
10-2 dB |
DATA SET AVAILABILITY |
Reduced: none |
OPERATING MODE AVAILABILITY |
LRM and SAR |
DATA ORIGIN |
1 Hz Ku/C-bands: none |
ADDITIONAL INFORMATION |
None |
PARAMETERS RELATED |
None |
PARAMETER DETAILED DESCRIPTION |
ESA's Global Land and Ocean Mission for GMES Operational Services |
Table 2. Sigma0 scaling factor
PARAMETER |
Tracker Range Estimate |
NETCDF NAME |
tracker_range_[x1]_[x2] |
DESCRIPTION |
LRM mode: tracker range corrected for: USO frequency drift (uso_cor_[x1]_[x2]), internal path correction (int_path_cor_[x1]_[x2]), Doppler correction (dop_cor_l1b_[x1]_[x2]) |
UNITS |
10-4 m. An offset of 700 000 m to be added to the value read from the netCDF file. |
DATA SET AVAILABILITY |
Reduced: none |
OPERATING MODE AVAILABILITY |
LRM and SAR |
DATA ORIGIN |
1 Hz Ku/C-bands: none |
ADDITIONAL INFORMATION |
None |
PARAMETERS RELATED |
Altitude on-board command (H0) computed with navigation/digital elevation model(h0_nav_dem_[x1]_[x2]). Units are on-board clock counter units (3.125/64x10-9 seconds). |
PARAMETER DETAILED DESCRIPTION |
ESA's Global Land and Ocean Mission for GMES Operational Services |
Table 3. Tracker range